Dopamine and serotonin are critical neuromodulators whose actions underlie learning, decision-making, and behavioral control. Degeneration of dopamine neurons underlies the progression of Parkinsonís disease; and disruptions in serotonin and dopamine signaling are believed to underlie many psychiatric conditions. We have recently published the worldís first sub-second measurements of dopamine release in humans. These measurements were made while participants (patients undergoing deep-brain stimulation implantation surgery for Parkinsonís disease) played a monetarily incentivized decision-making game. I will discuss our groupís recent technological achievements, which now (1) extend this technology to simultaneously measure dopamine and serotonin during active decision-making and (2) begin to provide real-time data about the roles these signals play during adaptive behavior in humans.